The present invention relates generally to weight lifting exercise machines, and is particularly concerned with an exercise arm apparatus for such a machine having pivotal linkage system for linking the arm to an exercise resistance such as a weight stack, springs, or other load.
The pulldown exercise is one of the most basic and oldest exercises in fitness. It is designed to exercise the major muscles in the upper back. The earliest machines designed to perform this exercise consisted of little more than a pulley mounted on the ceiling with a rope reeved around it. The rope was attached to a load at one end and a horizontal bar at the other end. In order to perform exercises, the exerciser would sit or kneel on the ground beneath the bar, reach up and grab the bar, and pull it downward, stopping close to their head at approximately shoulder level.
In an effort to improve comfort, freestanding machines with seats attached for the exerciser were soon designed. One such machine is described in U.S. Pat. No. 3,640,528 of Proctor. The major disadvantage in these machines is that it is difficult for the user to maintain strict form when performing the exercise. The bar is attached directly to a flexible line, such as a rope, cable, belt, chain or the like, and the user can therefore pull the bar off to one side or the other, or lean backward while pulling the bar downward, which could stress or strain the muscle in the lower back. Also, this machine has a reduced range of exercise motion. The single piece horizontal bar limits the amount of exercise travel because the user cannot pull it past their upper chest or back (depending on whether it is pulled down in front or behind the head). A further disadvantage is convenience and safety. The user must tilt their head either forwards or backwards at just the right moment in order to avoid hitting themselves with the bar.
The disadvantages of the original pulldown machines brought about the development of the rigid arm pulldown machine. This consists of a frame, a seat for the user mounted on the frame, a generally U shaped exercise arm equipped with handles set apart at a distance slightly greater than shoulder width, and a resistive force or load. The arm, which is resisted by the load, is pivotally connected to the frame and angles upward in the rest position, with the handles located high above the seat. In order to perform exercises, the seated user reaches up and grabs the handles, then pulls the arm downward slightly past shoulder level. The rigid arm pulldown works the same muscles as a traditional pulldown machine. However, because it does not have a free-swinging bar extending horizontally from hand-to-hand, it provides a safer, more restricted exercise movement with a greater range of travel.
Some rigid arm pulldown machines include a four-bar linkage system as a way to control the path of travel of the exercise arm, as in U.S. Pat. No. 5,1104,121 of Webb, or the resistance supplied to the exercise arm, as in U.S. Pat. No. 5,366,432 of Habing. The four-bar linkage system has four major components: a stationary member or frame, two pivoting members each pivotally connected to the stationary frame member at spaced positions, and a connecting link that is pivotally connected to the two pivoting members. One of the pivoting members acts as the exercise arm to be engaged by the user.
One disadvantage to the rigid arm design is the weight of the exercise arm. Because most of the arm is forward of the pivoting connection to the stationary frame member, it must be counter-balanced so that it will stay in the up or rest position when resistance is being removed or adjusted. This can be accomplished in several ways, such as attaching a weight to the rear end of the arm, i.e. the opposite side of the pivot to the handle, attaching springs to the rearward end of the arm to return it to the rest position, permanently pinning some weights in a stack of selectorized weights in an amount greater than the balance weight of the arm, or providing an amount of framework for the arm or arm assembly which is greater on the rearward side of the main pivot than on the handle side. Each of these options is subject to some disadvantages.
A weight attached directly to the rearward end of an exercise arm needs to increase in size and weight the closer it is placed to the pivot, or it will not offset the weight of the handle end of the arm. If the counterweight is placed close to the pivot, it will be larger and more expensive. When placed further from the pivot, the arm grows in length and the rear end travels in a large arc. This takes up more space and can pose a safety issue for anyone walking behind the machine. One example of a machine in which weight is attached to the rearward end of an exercise arm to act as a counter-balance is described in U.S. Pat. No. 5,263,914 of Simonson.
U.S. Pat. No. 5,437,589 of Habing is an example of a rigid arm pulldown machine using springs as a counter-balance to return the exercise arm to the rest position. Springs strong enough to offset the weight of the handle and allow for adequate handle travel can end up being fairly long and this will affect the design of the machine. Springs do not maintain an even resistance throughout the length of their stretch, which could affect the resistance and smoothness of motion felt by the user. Over time, springs tend to lose their tension, which would lessen their ability to counter-balance the exercise arm adequately. Additionally, springs tend to fatigue and ultimately break after repeated use, resulting in machine xe2x80x9cdown timexe2x80x9d, additional maintenance expense, and possible injury.
In some cases, a portion of the selector weight stack is permanently pinned to provide the required counter-balance weight, for example as shown in the brochure of Magnum Fitness. One disadvantage to such a system is that the amount of resistance available to a user is reduced. This results either in less weight for the weight stack or requires a heavier weight stack, increasing-the cost to manufacture the machine.
Some pulldown machines have used an increased size of framework for the arm assembly for counter-balance, as in U.S. Pat. No. 5,217,422 of Domzalski. This uses a complicated linkage system and increases both the size of the machine and the cost to produce it.
It is an object of the present invention to provide a new and improved exercise arm linkage system for an exercise apparatus.
According to one aspect of the present invention, an exercise apparatus is provided which comprises a stationary frame having a forward end and a rear end, an exercise arm assembly pivotally mounted on the frame, and an exercise resistance linked to the exercise arm assembly, the exercise arm assembly comprising a first, exercise arm pivotally connected to the frame for rotation about a first pivot axis, the first exercise arm having a forward portion projecting forwardly from the first pivot axis and a rear portion projecting rearwardly from the first pivot axis, a second arm pivotally connected to the frame for rotation about a second pivot axis spaced from the first pivot axis, and a connecting link member pivotally connected to the rear portion of the first arm and to the second arm, the connecting link member comprising a counter-weight of predetermined weight to counter-balance the forward portion of the first exercise arm into a rest position.
In an exemplary embodiment, the connecting link member is a solid metal bar of square, round or rectangular cross-section, such as a 2xe2x80x3 by 2xe2x80x3 solid steel bar or other bar of equivalent weight, rather than the typical, lighter flat bar or hollow tubing found in the prior art which will have little counter-balancing effect. This provides the necessary weight to offset the first or exercise arm and provides a safe, compact and cost efficient design, avoiding the need for expensive, add-on counterweights, springs, complicated linkage systems, or the like.
Both pivoting arms may be pivotally mounted on a single frame member of the frame, with the first, exercise arm spaced above the second arm and having handles at its forward end for engagement by a user, and the second arm or the connecting link member linked to the load or exercise resistance. The arrangement may be such that the connecting link member travels in substantially vertical, straight line as the arms are pivoted about their respective pivot axes. The second arm may be shorter in length than the first exercise arm such what the rearward extension of the assembly is reduced.
The exercise resistance in one example may be provided by weight plates removably mountable on the connecting link. In another example, a load-bearing cable linked to a weight stack or the like supplies the exercise resistance. The load-bearing cable may be linked to the second arm or to the end of the connecting link, such that it travels in a substantially straight line throughout the exercise motion. The load-bearing cable may be terminated at the exercise arm assembly, or may travel on to an additional exercise station. In the case of either removable weight plates or a load-bearing cable, the exercise resistance will travel in a substantially straight line, providing uniform resistance throughout the exercise motion.
Because the connecting link of a four-bar linkage system acts as the counter-weight in this invention, and travels in a substantially straight line rather than arcing up and out, the apparatus is safer and there is less risk of a counter-balance accidentally striking and injuring someone near the machine. The moving parts on a four-bar linkage system are much more visible, and hence more readily avoided, than a counter-weight attached to a free end of an exercise arm. The counter-balancing connecting link of this invention is attached to the rear ends of the two pivoting arms so that nothing protrudes past it.
The apparatus of this invention will be of relatively low cost to manufacture, due to its simplicity and reduced material requirements. In prior art arrangements where a large block of steel was required as a counter-balance, material expense is increased, and further machining is required to attach the block to the end of a pivot member or exercise arm. In contrast, with the present invention, the same amount of work is required to mount the connecting link as would be needed if the connecting link were made of hollow tubing, as in the past, and no additional parts need to be attached in order to provide the required counter-weight. Solid metal bar does not cost as much as a large block of steel or extra weight plates. This arrangement also does not require a portion of the weight stack to be permanently pinned, thereby providing more available exercise weight.
A further benefit of this arrangement is the consistent resistance delivered to the user. Because the connecting link travels in a substantially straight line, there is no resistance change or xe2x80x9ccamming overxe2x80x9d effect to the counter-balance, as would occur with a leverage type counter-balance which travels in an arcuate path. As the position of such a counter-balance changes along the path, there will be a slight variation in the counter-balancing effect which will be felt by the user. With a spring counter-balance as used in some prior art devices, there will also be a resistance change as the spring stretches. In the present invention, the load bearing cable will travel in a substantially straight line so that there is no xe2x80x9cdrop offxe2x80x9d in resistance felt by the user.